Motion image encoding method and motion image decoding method
The present invention provides a video coding method and a video decoding method which allow enhancement of coding efficiency and improvement in video quality. A video coding apparatus includes: a mode determination unit which determines a notification method for notifying a transform block size to be used in orthogonal transform of a current block to be either the implicit mode or the explicit mode, and outputs the ABT mode indicating the determined notification method; an orthogonal transformation unit which transforms the difference values between the input image and predicted image into frequency coefficients based on the transform block size determined in accordance with the determined notification method; a quantization unit which quantizes the frequency coefficients and output the quantized values; and a variable length coding unit which performs variable length coding on the quantized values, the ABT mode, and the like, so as to output a coded stream.
1. A video coding method for coding an input picture on a block-by-block basis so as to generate a coded stream, said method comprising:
determining, using a processor, a notification method for notifying a transform block size to be used in an orthogonal transform of a current block;
creating an adaptive block transform mode indicating the notification method;
generating the coded stream; and
adding the adaptive block transform mode to the coded stream;
wherein said determining includes determining, as the notification method, either (i) an implicit mode in which the transform block size is determined based on information regarding the current block or (ii) an explicit mode in which a transform size flag indicating the transform block size is added to each predetermined unit of blocks, and
wherein in the implicit mode, the transform block size is determined based on motion vectors of blocks adjacent to the current block.
2. The video coding method according to claim 1 ,
wherein in the implicit mode, the transform block size is determined to be 4×4 pixels in a case where a degree to which the motion vectors differ from each other is greater than or equal to a predetermined threshold value, and
wherein in the implicit mode, the transform block size is determined to be 8×8 pixels in a case where the degree to which the motion vectors differ from each other is less than the predetermined threshold value.
3. A video coding method for coding an input picture on a block-by-block basis so as to generate a coded stream, said method comprising:
determining, using a processor, a notification method for notifying a transform block size to be used in an orthogonal transform of a current block;
creating an adaptive block transform mode indicating the notification method;
generating the coded stream; and
adding the adaptive block transform mode to the coded stream;
wherein said determining includes determining, as the notification method, either (i) an implicit mode in which the transform block size is determined based on information regarding the current block or (ii) an explicit mode in which a transform size flag indicating the transform block size is added to each predetermined unit of blocks, and
wherein in the implicit mode, the transform block size is determined based on a quantization step used for quantization of the current block.
4. The video coding method according to claim 3 ,
wherein in the implicit mode, the transform block size is determined to be 8×8 pixels in a case where the quantization step is greater than or equal to a predetermined threshold value, and
wherein in the implicit mode, the transform block size is determined to be 4×4 pixels in a case where the quantization step is less than the predetermined threshold value.
5. The video coding method according to claim 1 , further comprising:
determining whether or not to apply an adaptive block transform in which the transform block size to be used in the orthogonal transform of the current block is (i) determined from among a plurality of transform block sizes and (ii) used;
performing said determining of the notification method when it is determined to apply the adaptive block transform;
creating an adaptive block transform flag indicating whether or not to apply the adaptive block transform; and
adding the adaptive block transform flag to the coded stream.
6. The video coding method according to claim 1 , further comprising:
determining the transform block size based on the notification method; and
coding the current block by performing the orthogonal transform on the current block using the determined transform block size.
7. A video decoding method for decoding a coded stream on a block-by-block basis, said method comprising:
obtaining, from the coded stream, an adaptive block transform mode indicating a notification method for notifying a transform block size used in an orthogonal transform of a current block;
identifying the notification method based on the adaptive block transform mode;
determining, using a processor, the transform block size based on the identified notification method; and
decoding the current block by performing an inverse orthogonal transform on the current block using the determined transform block size,
wherein the adaptive block transform mode indicates, as the notification method, either (i) an implicit mode in which the transform block size is determined based on information regarding the current block or (ii) an explicit mode in which a transform size flag indicating the transform block size is added to each predetermined unit of blocks, and
wherein in the implicit mode, the transform block size is determined based on motion vectors of blocks adjacent to the current block.
8. The video decoding method according to claim 7 ,
wherein in the implicit mode, the transform block size is determined to be 4×4 pixels in a case where a degree to which the motion vectors differ from each other is greater than or equal to a predetermined threshold value, and
wherein in the implicit mode, the transform block size is determined to be 8×8 pixels in a case where the degree to which the motion vectors differ from each other is less than the predetermined threshold value.
9. A video decoding method for decoding a coded stream on a block-by-block basis, said method comprising:
obtaining, from the coded stream, an adaptive block transform mode indicating a notification method for notifying a transform block size used in an orthogonal transform of a current block;
identifying the notification method based on the adaptive block transform mode;
determining, using a processor, the transform block size based on the identified notification method; and
decoding the current block by performing an inverse orthogonal transform on the current block using the determined transform block size,
wherein the adaptive block transform mode indicates, as the notification method, either (i) an implicit mode in which the transform block size is determined based on information regarding the current block or (ii) an explicit mode in which a transform size flag indicating the transform block size is added to each predetermined unit of blocks, and
wherein in the implicit mode, the transform block size is determined based on a quantization step used for quantization of the current block.
10. The video decoding method according to claim 9 ,
wherein in the implicit mode, the transform block size is determined to be 8×8 pixels in a case where the quantization step is greater than or equal to a predetermined threshold value, and
wherein in the implicit mode, the transform block size is determined to be 4×4 pixels in a case where the quantization step is less than the predetermined threshold value.
11. The video decoding method according to claim 7 , further comprising:
obtaining an adaptive block transform flag indicating whether or not an adaptive block transform, in which the transform block size to be used in the orthogonal transform of the current block is (i) determined from among a plurality of transform block sizes and (ii) used, is applied; and
obtaining the adaptive block transform mode when the adaptive block transform flag indicates that the adaptive block transform is applied.
12. A video coding apparatus which codes an input picture on a block-by-block basis so as to generate a coded stream, said apparatus comprising:
a processor;
a notification method determination unit operable to determine, using said processor, a notification method for notifying a transform block size to be used in an orthogonal transform of a current block;
a creation unit operable to create an adaptive block transform mode indicating the notification method; and
a coding unit operable to generate the coded stream and add the adaptive block transform mode to the coded stream,
wherein said notification method determination unit is operable to determine, as the notification method, either (i) an implicit mode in which the transform block size is determined based on information regarding the current block or (ii) an explicit mode in which a transform size flag indicating the transform block size is added to each predetermined unit of blocks, and
wherein in the implicit mode, the transform block size is determined based on motion vectors of blocks adjacent to the current block.
13. A video decoding apparatus which decodes a coded stream on a block-by-block basis, said apparatus comprising:
a processor;
an obtaining unit operable to obtain, from the coded stream, an adaptive block transform mode indicating a notification method for notifying a transform block size used in an orthogonal transform of a current block;
an identification unit operable to identify the notification method based on the adaptive block transform mode;
a determination unit operable to determine, using said processor, the transform block size based on the identified notification method; and
a decoding unit operable to decode the current block by performing an inverse orthogonal transform on the current block using the determined transform block size,
wherein the adaptive block transform mode indicates, as the notification method, either (i) an implicit mode in which the transform block size is determined based on information regarding the current block or (ii) an explicit mode in which a transform size flag indicating the transform block size is added to each predetermined unit of blocks, and
wherein in the implicit mode, the transform block size is determined based on motion vectors of blocks adjacent to the current block.
14. An integrated circuit for coding an input picture on a block-by-block basis so as to generate a coded stream, said circuit comprising:
a processor;
a notification method determination unit operable to determine, using said processor, a notification method for notifying a transform block size to be used in an orthogonal transform of a current block;
a creation unit operable to create an adaptive block transform mode indicating the notification method; and
a coding unit operable to generate the coded stream and add the adaptive block transform mode to the coded stream,
wherein said notification method determination unit is operable to determine, as the notification method, either (i) an implicit mode in which the transform block size is determined based on information regarding the current block or (ii) an explicit mode in which a transform size flag indicating the transform block size is added to each predetermined unit of blocks, and
wherein in the implicit mode, the transform block size is determined based on motion vectors of blocks adjacent to the current block.
15. An integrated circuit for decoding a coded stream on a block-by-block basis, said circuit comprising:
a processor;
an obtaining unit operable to obtain, from the coded stream, an adaptive block transform mode indicating a notification method for notifying a transform block size used in an orthogonal transform of a current block;
an identification unit operable to identify the notification method based on the adaptive block transform mode;
a determination unit operable to determine, using said processor, the transform block size based on the identified notification method; and
a decoding unit operable to decode the current block by performing an inverse orthogonal transform on the current block using the determined transform block size,
wherein the adaptive block transform mode indicates, as the notification method, either (i) an implicit mode in which the transform block size is determined based on information regarding the current block or (ii) an explicit mode in which a transform size flag indicating the transform block size is added to each predetermined unit of blocks, and
wherein in the implicit mode, the transform block size is determined based on motion vectors of blocks adjacent to the current block.
16. A video coding apparatus which codes an input picture on a block-by-block basis so as to generate a coded stream, said video coding apparatus comprising:
a processor;
a notification method determination unit operable to determine, using said processor, a notification method for notifying a transform block size to be used in an orthogonal transform of a current block;
a creation unit operable to create an adaptive block transform mode indicating the notification method; and
a coding unit operable to generate the coded stream and add the adaptive block transform mode to the coded stream,
wherein said notification method determination unit is operable to determine, as the notification method, either (i) an implicit mode in which the transform block size is determined based on information regarding the current block or (ii) an explicit mode in which a transform size flag indicating the transform block size is added to each predetermined unit of blocks, and
wherein in the implicit mode, the transform block size is determined based on a quantization step used for quantization of the current block.
17. A video decoding apparatus which decodes a coded stream on a block-by-block basis, said apparatus comprising:
a processor;
an obtaining unit operable to obtain, from the coded stream, an adaptive block transform mode indicating a notification method for notifying a transform block size used in an orthogonal transform of a current block;
an identification unit operable to identify the notification method based on the adaptive block transform mode;
a determination unit operable to determine, using said processor, the transform block size based on the identified notification method; and
a decoding unit operable to decode the current block by performing an inverse orthogonal transform on the current block using the determined transform block size,
wherein the adaptive block transform mode indicates, as the notification method, either (i) an implicit mode in which the transform block size is determined based on information regarding the current block or (ii) an explicit mode in which a transform size flag indicating the transform block size is added to each predetermined unit of blocks, and
wherein in the implicit mode, the transform block size is determined based on a quantization step used for quantization of the current block.
18. An integrated circuit for coding an input picture on a block-by-block basis so as to generate a coded stream, said circuit comprising:
a processor;
a notification method determination unit operable to determine, using said processor, a notification method for notifying a transform block size to be used in an orthogonal transform of a current block;
a creation unit operable to create an adaptive block transform mode indicating the notification method; and
a coding unit operable to generate the coded stream and add the adaptive block transform mode to the coded stream,
wherein said notification method determination unit is operable to determine, as the notification method, either (i) an implicit mode in which the transform block size is determined based on information regarding the current block or (ii) an explicit mode in which a transform size flag indicating the transform block size is added to each predetermined unit of blocks, and
wherein in the implicit mode, the transform block size is determined based on a quantization step used for quantization of the current block.
19. An integrated circuit for decoding a coded stream on a block-by-block basis, said circuit comprising:
a processor;
an obtaining unit operable to obtain, from the coded stream, an adaptive block transform mode indicating a notification method for notifying a transform block size used in an orthogonal transform of a current block;
an identification unit operable to identify the notification method based on the adaptive block transform mode;
a determination unit operable to determine, using said processor, the transform block size based on the identified notification method; and
a decoding unit operable to decode the current block by performing an inverse orthogonal transform on the current block using the determined transform block size,
wherein the adaptive block transform mode indicates, as the notification method, either (i) an implicit mode in which the transform block size is determined based on information regarding the current block or (ii) an explicit mode in which a transform size flag indicating the transform block size is added to each predetermined unit of blocks, and
wherein in the implicit mode, the transform block size is determined based on a quantization step used for quantization of the current block.